This example shows a large yellow smiley face rendered to fill the browser window, built as a React component. The face uses SVG primitives: a yellow circle with a black stroke, two eye circles, and a mouth path. The mouth shape is generated using the `d3.arc()` API with inner and outer radii and start/end angles. Instead of hardcoding values, dimensions are calculated dynamically from `window.innerWidth` and `window.innerHeight`. React renders the SVG, while D3 v5 provides the arc generator, with all elements positioned relative to the screen center.